public class Example4_8 {
   public static void main(String args[]) {
      Circle circle = new Circle();
      circle.setRadius(10);
      Circular circular = new Circular();
      System.out.println("circle的引用:"+circle);
      System.out.println("圆锥的bottom的引用:"+circular.bottom);
      circular.setHeight(5);
      circular.setBottom(circle);
      System.out.println("circle的引用:"+circle);
      System.out.println("圆锥的bottom的引用:"+circular.bottom);
      System.out.println("圆锥的体积："+circular.getVolme());
      System.out.println("修改circle的半径，bottom的半径同样变化");
      circle.setRadius(20);
      System.out.println("bottom的半径："+circular.getBottomRadius());
      System.out.println("重新创建circle,circle的引用将发生变化");
      circle = new Circle();
      System.out.println("circle的引用："+circle);
      System.out.println("但是不影响circular的bottom的引用");
      System.out.println("圆锥的bottom的引用："+circular.bottom);
   }
}
